Oxalic, tartaric, glyoxylic and erythronic acids are products having large present and potential commercial applications. In theory they are obtainable at low cost and in unlimited quantity from cellulosic raw materials.
In one procedure of potential application it is possible to manufacture these acids from wood or woody materials by (1) converting the material to cellulose e.g. paper pulp, (2) oxidizing the cellulose to dialdehyde cellulose, (3) oxidizing the dialdehyde cellulose to di- and tricarboxy celluloses and (4) hydrolyzing the di- and tricarboxy celluloses to a mixture of oxalic, tartaric, glyoxylic and erythronic acids. A process for effectuating the last of the above named steps is set forth and described in our copending application Ser. No. 628,887 filed Nov. 5, 1975, entitled HYDROLYZING DI- AND TRICARBOXY CELLULOSES WITH SULFUROUS ACID.
In another potentially available process carbohydrate materials are oxidized in aqueous solution by means of an oxidizing agent such as nitric acid, producing a mixture of oxalic, tartaric and other organic acids.
A problem is presented in isolating the individual acids from such mixtures. Prior art procedures for accomplishing this result are outlined in U.S. Pat. Nos. 2,319,020 and 2,470,841. However, such procedures have the common failing of requiring the use of expensive reagents in complicated and time consuming operational sequences. In addition, they do not produce the nearly quantitative yields required for the practical, low cost, commercial production of the organic acids in question.
It accordingly is the general purpose of the present invention to provide an economical, practical, low cost procedure for the substantially quantitative isolation of oxalic, tartaric, glyoxylic and erythronic acids, or any one or ones of such acids, from each other and from aqueous solutions in which they are contained in admixture with each other.